Fluids based on fluorocarbon compounds are widely used in many industrial devices, in particular air conditioning, heat pump or refrigeration devices. These devices have in common the fact that they are based on a thermodynamic cycle comprising the vaporization of the fluid at low pressure (in which the fluid absorbs heat); the compression of the vaporized fluid to a high pressure; the condensation of the vaporized fluid to liquid at high pressure (in which the fluid releases heat); and the expansion of the fluid in order to complete the cycle.
The compression step is carried out using a compressor, which may be, in particular, a centrifugal compressor.
The choice of a heat transfer fluid (which may be a pure compound or a mixture of compounds) is dictated, on the one hand, by the thermodynamic properties of the fluid and, on the other hand, by additional constraints, and in particular environmental constraints.
It is in this way that chlorinated compounds (chlorofluorocarbons and hydrochlorofluorocarbons) have the disadvantage of damaging the ozone layer. Henceforth, generally non-chlorinated compounds such as hydrofluorocarbons are therefore preferred to them.
In particular, many air conditioning systems currently operate with HFC-134a as heat transfer fluid. However, HFC-134a has a global warming potential (GWP) which is too high. It is therefore desirable to replace HFC-134a with another heat transfer fluid having a lower GWP.
However, any modification of the heat transfer fluid may pose problems in adapting the vapor compression cycle system. In particular, when the cycle uses a centrifugal compressor, the replacement of the heat transfer fluid may require a change of the centrifugal compressor itself or at the very least a modification of the operating parameters of the compressor liable to degrade the efficiency of the system or to accelerate wear phenomena.
Documents WO 97/17414 and U.S. Pat. No. 6,991,743 propose the replacement of dichlorodifluoromethane (CFC-12) with compositions comprising HFC-134a in cycles comprising a centrifugal compressor. The choice of substitute compositions is mainly made as a function of the molecular weight. However, the molecular weight is not in fact sufficiently predictive of the behavior of the various heat transfer fluids.
Document U.S. Pat. No. 5,076,064 proposes the replacement of trichlorofluoromethane (CFC-11) with compositions comprising, in particular, 1,1-dichloro-2,2,2-trifluoroethane (CFC-123) in cycles comprising a centrifugal compressor. The choice of the substitute compositions is mainly made as a function of the Mach number.
Documents WO 2005/108522 and WO 2007/126414 disclose mixtures of fluoroolefins and of other heat transfer compounds as heat transfer fluids. However, these documents do not identify any composition specifically suitable for a vapor compression system comprising a centrifugal compressor.
Document WO 2007/053697 also describes compositions based on fluoroolefins intended to be used as heat transfer fluids. Example 7 describes compounds suitable for replacing 1,2,2-trichlorofluoroethane (CFC-113) in cycles provided with a centrifugal compressor. The choice of the compounds is based on a calculation of theoretical rotational speed of the blades of the compressor. The approximations used in this calculation are however reserved for relatively heavy fluids.
Document WO 2009/018117 describes mixtures of fluoroolefins and of other heat transfer compounds as heat transfer fluids, especially as a replacement for HFC-134a. However, this document does not identify any composition specifically suitable for a vapor compression system comprising a centrifugal compressor.
Document WO 2009/151669 describes various heat transfer compositions based on specific lubricants and fluoroolefins.
None of the documents of the prior art proposes a heat transfer fluid as a replacement for HFC-134a in a vapor compression system comprising a centrifugal compressor, which both has a GWP below that of HFC-134a and guarantees the maintenance or even an improvement of the performances of the centrifugal compressor relative to HFC-134a.
There is therefore a real need to develop such a heat transfer fluid.